Catheter

ABSTRACT

The catheter  1  of the present invention has a tubular catheter body  2  made from a metal material. A groove  21  is formed in the outer periphery of the catheter body  2  in the longitudinal direction. This groove  21  is formed by plastically transforming the tubular wall of the catheter body  2  by plastic treatment. Thus, there is provided a catheter which has excellent followability and high ease of operation while maintaining torque transmissibility and pushability.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a catheter to be inserted into abody lumen, vessel or duct such as a blood vessel for use. The presentinvention also relates to a balloon catheter having a balloon in thedistal end portion thereof, and particularly, to a rapid-exchange typeballoon catheter.

[0003] 2. Description of the Related Art

[0004] In recent years, intravascular operations have been widelyperformed to treat a lesion part of a blood vessel by inserting acatheter into the blood vessel percutaneously without carrying out asurgical operation. In these operations, a catheter must be selectivelyinserted into an intricately bending, meandering or branching narrowblood vessel to position its distal end portion at the targeted site.

[0005] In general, in order to insert a catheter into the blood vesselpercutaneously, the catheter is made to reach the targeted site while aguide wire (introduction aid tool) is inserted into the lumen of thecatheter. On this occasion, generally, the catheter is preceded by aguide wire and advanced to the target site in the blood vessel.

[0006] To guide the catheter having the guide wire inserted therein intothe targeted site of the body, the operation of moving forward orbackward or turning the guide wire and the catheter is carried out froman end side in vitro thereof. This operation must be transmitted to thedistal end side of the catheter without fail. Therefore, torquetransmissibility and pushability are required for the catheter.

[0007] When the body portion (catheter body) of a relatively thincatheter having a small diameter to be applied to a narrow blood vesselis made from a synthetic resin material, it may have low stiffness or bereadily kinked, whereby the above-mentioned torque transmissibility andpushability may not be obtained fully. Therefore, the catheter body ofthe relatively narrow catheter is made of a metal tube having bendingelasticity.

[0008] However, when the catheter body is made of a metal tube, thedistal end side portion of the catheter body especially has too highflexural rigidity and lacks flexibility. Therefore, it is inferior infollow-up ability (followability) which enables it to follow thepreceding guide wire in the winding blood vessel smoothly and reliably.

[0009] A balloon catheter to be inserted into the blood vessel typifiedby a catheter used for PTCA (Percutaneous Transluminal CoronaryAngioplasty) (to be referred to as “PTCA catheter” hereinafter) has aguide wire lumen for inserting a guide wire which is formed along theentire length of the catheter in addition to a balloon lumen forinflating the balloon. Prior to the insertion of the catheter into theblood vessel, the guide wire is inserted into the guide wire lumen andthe distal end portion of the guide wire is guided to the targeted site(near a stricture in the blood vessel) together with the catheter insuch a manner that the distal end of the guide wire precedes thecatheter.

[0010] There are many variations of the PTCA catheter which differ inthe size of a balloon to be suited to a case of a disease such as thesize of the stricture site and the diameter of the blood vessel or toexpand the stricture site stepwise. After insertion into the bloodvessel, the work of exchanging the PTCA catheter may be necessary. Evenwhen a plurality of indwelling units for securing an inner diameter inthe blood vessel, called “stent”, are installed, the catheter may beremoved from and inserted into the blood vessel several times.

[0011] The exchange of the catheter described above is preferablycarried out while the guide wire is left in the blood vessel to reduce aburden on a patient, the operation time and the labor, to preventinfection, or the like.

[0012] However, since the guide wire lumen is formed along the entirelength of the conventional catheter as described above, in order toexchange the catheter from the in-vitro end side (proximal end side) ofthe guide wire while the guide wire is left in the blood vessel, thein-vitro end of the guide wire must be projected from the proximal endof the catheter to a length longer than the total length of thecatheter. That is, the length of the guide wire must be twice or morethe length of the catheter and there is a problem that such longprojecting guide wire reduces ease of the operation.

[0013] There is proposed a rapid-exchange type catheter having a guidewire lumen formed only in the distal end portion of the catheter, thatis, a catheter in which an opening at the distal end of the cathetercommunicates with a side hole formed at a position several centimetersaway from the opening toward the proximal end and this short lumen isengaged with a guide wire (EP 0397357 A1 (JP 4-9548 B)). This cathetercan be exchanged while the guide wire is left in the blood vesselwithout projecting the in-vitro end of the guide wire long from theproximal end of the catheter.

[0014] In order to guide the catheter to the targeted site in vivo whilethe guide wire is inserted in the guide wire lumen, as the blood vesselmeanders, the guide wire and the catheter must conform to the curvatureof the meandering blood vessel. In order to conform to this curvature,the operation of moving forward or backward or turning the guide wireand the catheter is carried out on the in-vitro end side. This operationmust be transmitted to the distal end side of the catheter without fail.To this end, torque transmissibility, pushability and kink resistanceare required for the catheter.

[0015] When the body portion (catheter body) of a relatively smallcatheter to be applied to a narrow blood vessel is made from a syntheticresin material, it may have low stiffness and be readily kinked, wherebythe above-mentioned torque transmissibility and pushability may not beobtained fully. Therefore, the catheter body of the relatively smallcatheter is made of a metal tube having bending elasticity.

[0016] However, when the catheter body is made of a metal tube, thedistal end side portion of the catheter body especially has too highflexural rigidity and lacks flexibility. Therefore, it is inferior infollow-up ability (followability) which enables it to follow thepreceding guide wire in the winding blood vessel smoothly and reliably.

SUMMARY OF THE INVENTION

[0017] It is an object of the present invention to provide a catheter,balloon catheter or rapid-exchange type catheter which easily winds in aspecific direction and has excellent followability and high ease ofoperation while securing torque transmissibility and pushability.

[0018] This object is attained by the present invention described as (1)to (11) in the following.

[0019] (1) A catheter having a tubular catheter body made from a metalmaterial, in which:

[0020] the catheter body has a groove formed in a longitudinal directionin the outer periphery of at least the distal end side portion thereofin such a manner that the tubular wall is caved in; and

[0021] the thickness of the tubular wall of the catheter body is almostconstant along the entire circumference including the groove formedportion.

[0022] (2) A balloon catheter including:

[0023] a tubular catheter body made from a metal material;

[0024] a balloon which can be inflated and deflated and is mounted onthe distal end side of the catheter body;

[0025] a balloon lumen which is formed of the lumen of the catheter bodyand that communicates with the inside of the balloon; and

[0026] a guide wire lumen which is open to the distal end side of theballoon, is surrounded by the tubular wall in the balloon and has aguide wire inserted from the distal end side of the balloon to theoutside of the catheter body therein, in which:

[0027] the catheter body has a groove formed in a longitudinal directionin the outer periphery of at least the distal end side portion thereofin such a manner that the tubular wall is caved in; and

[0028] the thickness of the tubular wall of the catheter body is almostconstant along the entire circumference including the groove formedportion.

[0029] (3) A catheter or balloon catheter according to the item (1) or(2) described above, in which the groove is formed along almost theentire length of the catheter body.

[0030] (4) A catheter or balloon catheter according to any one of theitems (1) to (3) described above which has a portion where the depth ofthe groove decreases continuously or stepwise toward the proximal end.

[0031] (5) A balloon catheter according to any one of the items (2) to(4) described above, in which at least the part of the guide wire can beinserted into the groove.

[0032] (6) A balloon catheter according to any one of the items (2) to(5) described above, in which an opening at the proximal end of theguide wire lumen is formed continuous to the distal end portion of thegroove.

[0033] (7) A balloon catheter according to any one of the items (2) to(6) described above, in which an inner tube is inserted into the balloonand the guide wire lumen is formed of the lumen of the inner tube.

[0034] (8) A catheter or balloon catheter according to any one of theitems (1) to (7) described above, in which the catheter body is madefrom stainless steel or pseudoelastic alloy.

[0035] (9) A catheter or balloon catheter according to any one of theitems (1) to (8) described above which further has a tubular member,made from a synthetic resin material, for covering the outer peripheryof at least the distal end side portion of the catheter body andextending farther in the distal end direction than the distal end of thecatheter body.

[0036] (10) A catheter or balloon catheter according to any one of theitems (1) to (9) described above, in which plural slits are formed inthe tubular wall of the distal end side portion of the catheter body andextend in a direction almost perpendicular to the longitudinal directionof the catheter body.

[0037] (11) A catheter or balloon catheter according to any one of theitems (1) to (10) described above, in which spiral slits are formed inthe tubular wall of the distal end side portion of the catheter body andin which the spiral pitch between the spiral slits become smallercontinuously or stepwise toward the distal end.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In the accompanying drawings:

[0039]FIG. 1 is a perspective view of Embodiment 1 of a catheter of thepresent invention (guide wire is inserted into a lumen);

[0040]FIG. 2 is a sectional view (transverse sectional view) taken alongthe line X-X of FIG. 1;

[0041]FIG. 3 is a perspective view of a catheter body of the cathetershown in FIG. 1;

[0042]FIG. 4 is a perspective view of a catheter body in Embodiment 2 ofthe catheter of the present invention;

[0043]FIG. 5 is a perspective view of a catheter body in Embodiment 3 ofthe catheter of the present invention;

[0044]FIG. 6 is a plan view of Embodiment 4 of the catheter of thepresent invention;

[0045]FIG. 7 is a sectional view (transverse sectional view) taken alongthe line Y-Y of FIG. 6;

[0046]FIG. 8 is a sectional view (transverse sectional view) taken alongthe line Z-Z of FIG. 6;

[0047]FIG. 9 is a graph showing an actual data on load and the amount ofdeflection in a three-point bending test of a metal tube on the verticalaxis and the horizontal axis, respectively;

[0048]FIG. 10 is a perspective view showing a balloon catheter ofEmbodiment 5 of the present invention inserted in a lumen of a guidingcatheter;

[0049]FIG. 11 is a longitudinal sectional view of the distal end portionof the catheter shown in FIG. 10;

[0050]FIG. 12 is a sectional view (transverse sectional view) takenalong the line X-X of FIG. 10; and

[0051]FIG. 13 is a sectional view (transverse sectional view) takenalong the line Y-Y of FIG. 11.

DETAILED DESCRIPTION OF THE INVENTION

[0052] A catheter of the present invention will be described in detailhereinafter based on preferred embodiments shown in the accompanyingdrawings.

[0053] <Embodiment 1>

[0054]FIG. 1 is a perspective view of Embodiment 1 of a catheter of thepresent invention (a guide wire is inserted into a lumen of thecatheter), FIG. 2 is a sectional view taken along the line X-X of FIG. 1(transverse sectional view), and FIG. 3 is a perspective view of acatheter body of the catheter shown in FIG. 1. In the followingdescription, the right side (side close at hand of the operation ofinserting into the body) of each figure is referred to as “proximal end”and the left side (distal end side to be inserted into the body) isreferred to as “distal end”.

[0055] The catheter 1 shown in FIG. 1 includes a small and long catheterbody 2 having bending elasticity and a hub 4 mounted to the proximal endof the catheter body 2. The constitution of each element of the catheterwill be described hereinafter.

[0056] The catheter body 2 is inserted into a body lumen, vessel or ductsuch as a blood vessel (to be typified by a blood vessel hereinafter)and is tubular. A tubular lumen (lumen) 23 is formed in the catheterbody 2 from the distal end to the proximal end thereof. When thecatheter body 2 is to be inserted into the blood vessel, a guide wire100 to be described below is inserted into the tubular lumen 23. Thetubular lumen 23 is also used as the passage of a liquid such asphysiological saline, medical fluid, cleaning fluid, contrast medium orbody fluid (such as blood).

[0057] This catheter body 2 is made from a metal material. Thus, thecatheter body 2 has higher rigidity (flexural rigidity and torsionalrigidity) than a catheter body made from a synthetic resin material(plastic). Therefore, the catheter body 2 has high stiffness even whenits outer diameter is relatively small. As a result, the catheter 1becomes excellent in torque transmissibility that torque applied fromthe proximal end can be transmitted to the distal end without fail andin pushability that an operator's push-in force for advancing thecatheter in the blood vessel can be transmitted to the distal end sidefrom the proximal end side without fail. It also becomes excellent inkink resistance.

[0058] That is, the catheter 1 of the present invention has high ease ofoperation even when the outer diameter of the catheter body 2 isrelatively small, whereby it can be preferably inserted into arelatively narrow blood vessel, in particular. The outer diameter(average outer diameter) of the catheter body 2 is not particularlylimited but preferably about 0.2 to 5 mm, more preferably about 0.3 to 3mm. The inner and outer diameters of the catheter body 2 may change inthe longitudinal direction.

[0059] The length of the catheter body 2 is not particularly limited andis suitably determined according to the use site of the catheter 1 and acase of a disease but generally, it is preferably about 80 to 200 cm.

[0060] The structural material of the catheter body 2 may be a metalmaterial but preferably a pseudoelastic alloy (super elastic alloy) suchas Ni—Ti alloy or stainless steel from the viewpoints of physicalproperties and safety. That is, the pseudoelastic alloy or stainlesssteel is readily returned to its original form by the removal of stress.The pseudoelastic alloy includes what is obtained by hot processing orcold processing, what is obtained by both hot processing and coldprocessing, and further what is obtained by another processing if itreturns to its original form after transformation. Therefore, itincludes what has almost constant stress even when distortion increasesand what has increasing distortion as stress grows in astress-distortion curve.

[0061] As shown in FIG. 1 and FIG. 2, a single groove (depression) 21 isformed in the outer periphery (side surface) of the catheter body 2 inthe longitudinal direction (axial direction) of the catheter body 2 insuch a manner that the tubular wall is caved in.

[0062] The sectional form of the groove 21 is almost arcuate in thisembodiment. The sectional form is not limited to this and may beV-shaped, U-shaped, rectangular, oval (semi-oval), or the like.

[0063] The groove 21 is formed by plastically processing the tubularwall of the catheter body 2 having a circular section to plasticallytransform it. This plastic processing can be easily carried out by thefollowing methods, for instance. (1) The method of which the unprocessedcatheter body 2 is inserted into a flask having a semi-circular sectionand an inner periphery with the same curvature as that of the outerperiphery (side surface) of the catheter body 2, a jig (such as a pin)having a projection corresponding to the groove 21 is installed at aposition opposite to the flask, and the catheter body 2 is movedrelative to the flask and the jig so that it is pulled out in thelongitudinal direction (axial direction) from between the flask and thejig while the jig is applied to the catheter body 2 to form the groove21 in the longitudinal direction gradually. (2) The method of which amile mold having a projecting rib corresponding to the groove 21 ispressed against the outer periphery of the catheter body 2 supported ina flask and the groove 21 equal to the length of the projecting rib isformed in one operation.

[0064] Since the tubular wall of a portion which has been pressed by theprojection of the above-mentioned jig or the projecting rib of theabove-mentioned male mold in the plastic processing escapes toward thelumen side of the catheter body 2 to form a projection 22, the thicknessof the tubular wall of the catheter body 2 is almost constant along theentire circumference of the tube including the groove 21 formed portion.As a result, the strength of the groove 21 formed portion is not reducedand even when the thickness of the tubular wall of the catheter body 2is relatively small, the deformation, damage, or the like of the groove21 formed portion can be effectively prevented.

[0065] Further, when the catheter body 2 is made from a pseudoelasticalloy, the groove 21 may be formed simultaneously with cold processingor hot processing or before or after cold processing or hot processing.

[0066] Since the above-mentioned groove 21 is formed in the catheterbody 2, it has a property (characteristic) that its flexural rigiditydiffers according to its bending direction. That is, when the catheterbody 2 is bent upward so that the groove 21 formed portion is located onthe inner side (state shown by A in FIG. 3), the flexural rigidity ofthe catheter body 2 is lower than that when it is bent downward so thatthe groove 21 formed portion is located on the outer side (state shownby B in FIG. 3) or when it is bent sideways so that a portion 90° awayfrom the groove 21 formed portion is positioned on the inner side (orouter side) (state shown by C and D in FIG. 3). Thus, the catheter body2 of the groove 21 formed portion is selectively readily bent in thedirection shown by A in FIG. 3.

[0067] As the catheter body 2 of the catheter 1 has the above-mentionedproperty, it has excellent follow-up ability (to be referred to as“followability” hereinafter) so that it can be inserted along thepreceding guide wire 100 in the winding blood vessel smoothly andreliably. This is because when the catheter body 2 is to be inserted andadvanced along the preceding guide wire 100, the catheter 1 is turnedsuch that the groove 21 formed portion is positioned on the inner sideof curvature in conformity to the curvature of the intricately branchingand winding blood vessel, whereby the catheter body 2 is readily bent inaccordance with the curvature of the blood vessel and thus can beinserted and advanced smoothly and reliably.

[0068] Thus, the catheter 1 exhibits excellent followability. Further,as described above, the catheter body 2 of the catheter 1 has highstiffness with relatively high rigidity so that the catheter 1 hasexcellent torque transmissibility and pushability. That is, the catheter1 of the present invention has excellent torque transmissibility andpushability as well as excellent followability. Thus, it has extremelyhigh ease of operation.

[0069] The inventor of the present invention conducted the followingthree-point bending test on a metal tube to prove that the flexuralrigidity of the catheter body 2 is changed according to its bendingdirection by the formation of the groove 21 as described above. In this3-point bending test, the amount of deflection was measured when themetal tube was bent at 3 points under the following conditions.

[0070] <Metal Tube>

[0071] material: SUS304, outer diameter: 0.55 mm, inner diameter: 0.33mm, thickness: 0.11 mm, depth of groove 21: 0.09 mm

[0072] <Bending Conditions>

[0073] Fulcrum punch diameter: 5 mm, distance between fulcra: 10 mm,bending speed: 1 mm/min, maximum load: 0.98 kgf

[0074]FIG. 9 is a graph in which an actual measurement data on load andthe amount of deflection obtained in the above-mentioned three-pointbending test are plotted on the vertical axis and the horizontal axis bya dotted line (measurement) and a solid line (after adjusting the nullpoint). FIG. 9 shows data obtained (1) when the catheter was bent upward(state shown by A in FIG. 3), (2) when it was bent downward (state shownby B in FIG. 3), (3) when it was bent sideways (state shown by C or D inFIG. 3) and (4) when there was no groove (normal: before a groove wasformed). As understood from the results of null point-adjusted solidlines in FIG. 9, the amounts of deflection under a load of 0.98 kgf inthese four cases are given below (the larger the amount of deflection,the lower the flexural rigidity becomes).

[0075] (1) Upward: 0.45 mm

[0076] (2) Downward: 0.33 mm

[0077] (3) Sideways: 0.30 mm

[0078] (4) No groove: 0.29 mm

[0079] It was found from the results of this three-point bending testthat flexural rigidity when the metal tube was bent upward so that thegroove 21 formed portion was located on the inner side was lower thanthat when it was bent in other directions. It was also found thatflexural rigidity when it was bent downward and sideways was almost thesame as that when there was no groove.

[0080] In this embodiment, the groove 21 is formed along almost theentire length of the catheter body 2. However, in the present invention,the groove 21 may be formed in part of the catheter body 2, for example,only in the distal end side portion of the catheter body 2.

[0081] Further, the sectional form, maximum depth, width and the like ofthe groove 21 may be constant or may vary in the longitudinal directionof the catheter body 2.

[0082] As shown in FIG. 1, X-ray impermeable markers 5 are formed on theouter periphery of the distal end of the catheter body 2. Thus, theposition of the distal end of the catheter body 2 can be confirmed byobservation through a fluoroscope. In the illustrated constitution, theX-ray impermeable markers 5 are formed by winding a thin wire of gold,silver, platinum, tungsten or the like. The form of the markers is notparticularly limited and may be, for example, sheet-like, band-like,C-shaped ring, or the like.

[0083] Furthermore, a layer of a hydrophilic polymer material (notshown) having lubricity in a moist state is preferably formed on theouter periphery of the catheter body 2. This reduces friction when thecatheter 1 is inserted, whereby the catheter 1 can be inserted smoothly,thereby improving ease of operation and safety.

[0084] The above-mentioned catheter body 2 is used by being insertedinto a guiding catheter (not shown) or contrast catheter as requiredwhen it is inserted into the blood vessel.

[0085] As shown in FIG. 1, a hub 4 is firmly fixed to the proximal endportion of the catheter body 2 liquid tightly, for instance. The lumenof the hub 4 communicates with the proximal end of the tubular lumen 23of the catheter body 2.

[0086] The hub 4 serves as a port for inserting the guide wire 100 intothe tubular lumen 23 of the catheter body 2, as a port for injecting aliquid such as a medical fluid into the tubular lumen 23, and the like.The hub 4 also serves as a grip when the catheter body 2 is operated.

[0087] The structural material of the hub 4 is not particularly limitedand may be, for example, a resin material such as polyvinyl chloride,polyethylene, polypropylene, polycarbonate, polymethyl methacrylate oran acrylonitrile-styrene-butadiene copolymer, or a metal material suchas stainless steel or titanium.

[0088] The guide wire 100 is a wire material having bending elasticity,and its structural material is not particularly limited and may be, forexample, a plastic, pseudoelastic (super elastic) alloy (such as Ni—Tialloy) or metal material such as stainless steel.

[0089] All or part of the surface of the guide wire 100 is preferablysubjected to a treatment for providing lubricity.

[0090] The distal end portion 101 of the guide wire 100 is bent in itsnatural state (external force is not applied). When a blood vessel isselected, the guide wire 100 and the catheter 1 are moved forward orbackward relative to each other to change the length of projection ofthe distal end portion 101 of the guide wire 100 from the opening at thedistal end of the catheter body 2 according to the situation.

[0091] That is, making use of the curvature of the distal end portion101 of the guide wire 100, the direction of the curvature is changed tothe direction of the targeted blood vessel by rotation to insert theguide wire 100 into the targeted blood vessel. At this point, a portionprojecting from the catheter body 2 of the guide wire 100 is greatlybent in most cases. The position of the groove 21 of the catheter body 2is turned in conformity to the bent guide wire 100 so that the groove 21is located on the depressed side (inner side) of the curvature of theguide wire 100. Accordingly, as excessive force is not applied to thecurvature of the guide wire 100, the guide wire 100 is prevented frombeing removed from the targeted blood vessel.

[0092] Thus, in the present invention, the distal end portions of theguide wire 100 and the catheter body 2 can be bent in many ways bycombining the rotation of the catheter 1 with the relative forward orbackward movement of the guide wire 100 and the catheter 1. In thepresent invention, the use of these various bending states makes itpossible to move forward the guide wire 100 and the catheter body 2 inthe targeted direction smoothly and readily while flexibly coping withthe complex shape of the blood vessel such as curved or branched.

[0093] A description is subsequently given of an example of usage of thecatheter 1.

[0094] The guide wire 100 is inserted into the tubular lumen 23 of thecatheter body 2 in advance.

[0095] Subsequently, an unshown guiding catheter or contrast catheter ispercutaneously inserted close to the targeted site of the blood vessel(to be referred to as “targeted site” hereinafter) by a Seldinger methodor the like using an unshown guide wire.

[0096] Next, after the above-mentioned guide wire is pulled out, thecatheter body 2 of the catheter 1 of the present invention is insertedinto the above-mentioned guiding catheter (contrast catheter), precededby a new guide wire 100, until its distal end portion reaches thetargeted site.

[0097] When the distal end portion of the catheter body 2 reaches thetargeted site, the guide wire 100 is pulled out from the catheter body2.

[0098] Thereafter, an injection device such as a syringe, for instance,is connected to the hub 4 to inject a contrast medium or medical fluid.Thus, the contrast medium or medical fluid is injected into the bloodvessel from the distal end of the catheter body 2 through the lumen ofthe hub 4 and the tubular lumen 23 of the catheter body 2 in the statedorder.

[0099] After the above operation has ended, the catheter body 2 ispulled out from the blood vessel together with the above-mentionedguiding catheter (contrast catheter).

[0100] <Embodiment 2>

[0101]FIG. 4 is a perspective view of a catheter body according toEmbodiment 2 of the catheter of the present invention. In FIG. 4, inorder to make it more understandable, the length in the longitudinaldirection of the catheter body 2 a is shortened.

[0102] With reference to this figure, Embodiment 2 of the catheter ofthe present invention will be described hereinafter, focusing on thedifference between the above-mentioned embodiment and this embodiment.The explanation of the same items is omitted.

[0103] This embodiment is identical to the above-mentioned Embodiment 1except that the depth (maximum depth) of the groove 21 of the catheterbody 2 a decreases continuously (progressively reduces) toward theproximal end of the catheter body 2 a.

[0104] In the catheter body 2 a of this embodiment, the depth of thegroove 21 becomes relatively larger toward the distal end and relativelysmaller toward the proximal end. As a result, the catheter body 2 abecomes more flexible with lower flexural rigidity toward the distal endthereof when it is bent upward so that the groove 21 formed portion islocated on the inner side, and the difference in ease of bending betweenthe direction of bending upward and other directions becomes smallertoward the proximal end thereof. Therefore, more excellent followabilityis obtained on the distal end side of the catheter body 2 a and higherstiffness and more excellent torque transmissibility and pushability canbe obtained on the proximal end side of the catheter body 2 a. That is,more excellent ease of operation can be obtained in this embodiment.

[0105] The depth of the groove 21 of the catheter body 2 a may bepartially constant in the longitudinal direction. The depth of thegroove 21 may also be null in part of the catheter body 2 a. That is,there may be no groove 21 in part of the catheter body 2 a.

[0106] <Embodiment 3>

[0107]FIG. 5 is a perspective view of a catheter body according toEmbodiment 3 of the catheter of the present invention. In FIG. 5, inorder to make it more understandable, the length in the longitudinaldirection of the catheter body 2 b is shortened.

[0108] With reference to this figure, Embodiment 3 of the catheter ofthe present invention will be described hereinafter, focusing on thedifference between the above-mentioned embodiment and this embodiment.The explanation of the same items will be omitted.

[0109] This embodiment is identical to the above-mentioned Embodiment 1except that the depth (maximum depth) of the groove 21 in the catheterbody 2 b decreases stepwise (progressively reduces) toward the proximalend of the catheter body 2 b.

[0110] In the catheter body 2 b of this embodiment, the depth of thegroove 21 decreases in plural stages (three stages in the illustratedconstitution) toward the proximal end. That is, the depth of the groove21 is relatively large on the distal end side of the catheter body 2 b,relatively small on the proximal end side, and intermediate in themiddle portion between them. Accordingly, the same effect as inEmbodiment 2 can be obtained in this embodiment.

[0111] Further, since portions having the same depth of the groove 21have the same flexibility, the depth and length of the groove 21 aresuitably changed according to the curvature of the targeted site,thereby making it possible to easily obtain a catheter suitable for allkinds of operations.

[0112] <Embodiment 4>

[0113]FIG. 6 is a plan view of Embodiment 4 of the catheter of thepresent invention, FIG. 7 is a sectional view (transverse sectionalview) taken along the line Y-Y of FIG. 6, and FIG. 8 is a sectional view(transverse sectional view) taken along the line Z-Z of FIG. 6.

[0114] With reference to these figures, Embodiment 4 of the catheter ofthe present invention will be described hereinafter, focusing on thedifference between the above-mentioned embodiments and this embodiment.The explanation of the same items will be omitted.

[0115] This embodiment is identical to the above-mentioned Embodiment 1except that it has a tubular member 3 for covering the outer peripheryof the catheter body 2 and that plural slits 24 are formed in thetubular wall of the distal end portion of the catheter body 2.

[0116] As shown in FIG. 6 and FIG. 7, the tubular (cylindrical) member 3for covering the outer periphery of the catheter 1′ of this embodimentis formed along the entire length of the catheter body 2.

[0117] The tubular member 3 is made from a synthetic resin material andhas flexibility. Examples of the synthetic resin material constitutingthe tubular member 3 include: polyolefins such as polypropylene,polyethylene and an ethylene-vinyl acetate copolymer; polyesters such aspolyethylene terephthalate (PET) and polybutylene terephthalate (PBT);fluorine-based resins such as polytetrafluoroethylene and anethylene-tetrafluoroethylene copolymer; resins having flexibility suchas polystyrene-based resin, polyamide, polyurethane and polyimide;polyamide elastomer, polyester elastomer, polyurethane elastomer,polystyrene elastomer and fluorine-based elastomer, or a combination oftwo or more out of these (such as a laminate consisting of plural layersand polymer blends thereof). Since the tubular member 3 is made from asoft material having higher flexibility than the catheter body 2, theresistance of the tubular member 3 can be substantially ignored when thecatheter body 2 is bent.

[0118] In this embodiment, as the outer periphery of the catheter body 2is covered with the tubular member 3 having such flexibility, a stimulusto the inner wall of the blood vessel can be further reduced, therebyincreasing safety.

[0119] Further, in the catheter 1′, the tubular member 3 extends fartherthan the distal end 25 of the catheter body 2 in the forward enddirection. That is, as shown in FIG. 8, the distal end portion of thecatheter 1′ is devoid of the catheter body 2 and composed only of thetubular member 3. Thus, the distal end portion of the catheter 1′ hashigher flexibility and can further reduce a stimulus to the inner wallof the blood vessel, thereby making it possible to obtain higher safety.Followability can also be further improved. The length of a portiondevoid of the catheter body 2 of the distal end portion is not limitedbut is preferably 2 to 300 mm.

[0120] The outer periphery of the tubular member 3 is preferably coveredwith a lubricant layer (not shown) of a hydrophilic (or water-soluble)polymer material. Thus, when the outer periphery of the tubular member 3contacts blood, physiological saline, or the like, the frictioncoefficient decreases and lubricity is provided, thereby furtherenhancing the slidability of the catheter 1′, resulting in furtherimproved torque transmissibility, pushability and safety.

[0121] The tubular member 3 is not limited to the one covering the totallength of the catheter body 2 but may be the one covering at least partof the outer periphery of distal end side of the catheter body 2. Inthis case, the same effect as above can be obtained.

[0122] Further, as shown in FIG. 6, in this embodiment, plural slits 24are formed in the tubular wall of a predetermined range on the distalend side of the catheter body 2. In the illustrated constitution, theslits 24 extend in a direction substantially perpendicular to thelongitudinal direction of the catheter body 2 and are arranged almostparallel to one another at predetermined intervals. At the slit 24formed sites, the flexibility of the catheter body 2 becomes high,whereby the catheter 1′ can obtain higher followability.

[0123] The provision of the tubular member 3 prevents the contrastmedium or medical fluid injected into the tubular lumen 23 from leakingfrom the slits 24.

[0124] Further, spiral slits may be formed in the tubular wall of thedistal end side portion of the catheter body 2 in place of the pluralslits 24. The same effect as above can be obtained in this way as well.In this case, these spiral slits are preferably formed in such a mannerthat the spiral pitch (interval) between the spiral slits becomessmaller continuously or stepwise toward the distal end. Thus, the distalend side portion of the spiral slit formed portion can be made moreflexible.

[0125] Furthermore, the slits may be formed in such a manner that theyextend in the longitudinal direction of the catheter body 2.

[0126] <Embodiment 5>

[0127]FIG. 10 is a perspective view showing a balloon catheter (to besimply referred to as “catheter” hereinafter) of Embodiment 5 of thepresent invention inserted in a lumen of a guiding catheter, FIG. 11 isa longitudinal sectional view of the distal end portion of the cathetershown in FIG. 10, FIG. 12 is a sectional view (transverse sectionalview) taken along the line X-X of FIG. 10, and FIG. 13 is a sectionalview (transverse sectional view) taken along the line Y-Y of FIG. 11.The perspective view of a catheter body of the catheter shown in FIG. 10is shown in FIG. 3.

[0128] The catheter 31 shown in FIG. 10 is a rapid-exchange type ballooncatheter which includes a catheter body 32 having flexural elasticity,an inflatable and deflatable balloon (expandable body) 33 which ismounted on the distal end side of the catheter body 32, and a hub 4mounted on the proximal end side of the catheter body 32. Theconstitution of each part will be described hereinbelow.

[0129] The catheter body 32 is made from a metal material and istubular. Thus, the catheter body 32 has higher rigidity (flexuralrigidity and torsional rigidity) than a catheter body made from asynthetic resin material (plastic). Therefore, the catheter body 32 hashigh stiffness even when its outer diameter is relatively small. As aresult, the catheter 31 has excellent torque transmissibility so thattorque applied from the proximal end side is transmitted to the distalend side without fail and excellent pushability so that an operator'spush-in force for advancing the catheter in the blood vessel can betransmitted from the proximal end side to the distal end side withoutfail.

[0130] That is, the catheter 31 of the present invention obtainsexcellent ease of operation even when the outer diameter of the catheterbody 32 is relatively small and is therefore particularly suitable foruse as a catheter having a relatively small diameter which can beinserted into a relatively narrow blood vessel. Thus, the outer diameter(average outer diameter) of the catheter body 32 is not particularlylimited but is preferably about 0.2 to 3 mm, and more preferably about0.3 to 2 mm. The outer and inner diameters of the catheter body 32 maychange in the longitudinal direction.

[0131] Further, the length of the catheter body 32 is not particularlylimited and suitably determined according to the site of using thecatheter 31 and a case of a disease. In general, it is preferably about100 to 200 cm.

[0132] As shown in FIG. 11, the lumen 23 of the catheter body 32constitutes a balloon lumen 11 which communicates with the inside of aballoon 33 to be described below. The balloon lumen 11 serves as apassage for supplying a working fluid for inflating and deflating theballoon 33 into the inside space of the balloon 33.

[0133] In the present invention, the provision of the groove 21contributes to the reduction of the diameter of the guiding catheter200. That is, since the guide wire 100 is received in the groove 21 inthe catheter 31 as shown in FIG. 12, there is no need to form a spacefor inserting the guide wire 100 between the outer periphery of thecatheter body 32 and the inner periphery of the guiding catheter 200,whereby the guiding catheter 200 may have almost the same small innerdiameter as the outer diameter of the catheter body 32. Accordingly, theguiding catheter 200 and the catheter 31 can be inserted (introduced)into a narrower blood vessel.

[0134] Further, since the guide wire 100 is received in the groove 21,the movement in the transverse direction of the guide wire 100 withrespect to the catheter 31 is fixed and a play can be eliminated. Sincethe guide wire 100 thus displaces together with the catheter 31 at thetime of operating the catheter 31, the above-mentioned torquetransmissibility and pushability become more excellent.

[0135] Furthermore, this groove 21 also serves as a guide passage formoving the guide wire 100 therealong.

[0136] In this embodiment, the groove 21 is formed along almost theentire length of the catheter body 32. In the present invention, thegroove 21 may be formed only in the distal end side portion of thecatheter body 32.

[0137] The sectional form, maximum depth, width and the like of thegroove 21 may be constant or may vary in the longitudinal direction ofthe catheter body 32.

[0138] As shown in FIG. 11, the balloon 33 is composed of a cylindricalfilm member and connected (fixed) to the distal end portion of thecatheter body 32 by a cylindrical connection member 12. The balloonlumen 11 communicates with the inside of the balloon 33 through thelumen of the connection member 12 from the lumen of the catheter body32.

[0139] The proximal end portion of the balloon 33 is sealed to the outerperiphery of the distal end portion of the connection member 12 airtightly or liquid tightly. The distal end portion of the balloon 33 issealed to the outer periphery of the distal end portion of the innertube 35 to be described below air tightly or liquid tightly. The sealingof these portions is carried out by fusion bonding or bonding with anadhesive, for example.

[0140] The balloon 33 is shriveled and folded before it is inflated(deflated). It is inflated when a working fluid is supplied into theinside of the balloon 33 (state shown in FIG. 10 and FIG. 11).

[0141] The structural material of the balloon 33 is a polymer material(particularly, a thermoplastic resin). In this case, the balloon 33 hasflexibility as a whole but it is preferably made from a material havingrelatively low elasticity (elongation).

[0142] Examples of the structural material of the balloon 33 includepolyester resins such as polyethylene terephthalate and polybutyleneterephthalate; olefin-based resins such as polyester elastomer,polyethylene and polypropylene; or those obtained by crosslinking theseresins (particularly, crosslinking by exposure to an electron beam);vinyl chloride resin; polyamide-based resins such as nylon 11, nylon 12and nylon 610; polyamide elastomer; polyurethane resin; anethylene-vinyl acetate copolymer; or those obtained by crosslinkingthese polymers; or polymer blends and polymer alloys containing at leastone of these.

[0143] Further, the balloon 33 may be composed of a laminate consistingof plural films of these materials. In this case, the laminate can beobtained by co-extrusion molding of layers or assembling layers togetherby adhesion bonding, fusion bonding, or the like, or forming one layeron another layer by coating, for instance. A soft resin layer, layer ofa lubricant material, layer of an antithrombic material, or the like mayalso be formed on the external side or internal side of a layer composedof one of the above-mentioned materials.

[0144] The structural material of the balloon 33 may contain, forexample, an antithrombic material such as heparin, prostaglandin,uroxinase or an arginine derivative.

[0145] The tubular inner tube 35 is arranged and inserted into theinside (inner side) of the balloon 33 and the connection member 12. Aguide wire lumen 51 for inserting the guide wire 100 is formed in thelumen of the inner tube 35.

[0146] The distal end portion of the guide wire lumen 51 (inner tube 35)is open on the distal end side (distal end portion) of the balloon 33and the proximal end portion of the guide wire lumen 51 (inner tube 35)is open near a bonding portion between the catheter body 32 and theconnection member 12. That is, the guide wire lumen 51 communicates withthe distal end side and the proximal end side of the balloon 33.

[0147] The guide wire 100 is inserted into the guide wire lumen 51, thedistal end side of the guide wire 100 projects from the opening 53 atthe distal end of the guide wire lumen 51, and the proximal end side ofthe guide wire 100 is exposed to the outside of the catheter 31 throughthe opening 52 at the proximal end of the guide wire lumen 51 and issituated in the groove 21 almost parallel to the catheter body 32.

[0148] X-ray impermeable markers 15 showing the boundaries between thecylindrical portion and the conical portions of the balloon 33 when theballoon 33 is inflated are formed on the outer periphery of the innertube 35. The X-ray impermeable markers 15 are made of, for example, athin (having a small diameter) wire, band, or the like of gold, silver,platinum, tungsten, etc.

[0149] Further, as shown in FIG. 13, the proximal end portion of theinner tube 35 is inserted into the distal end portion of the groove 21,and the inner periphery of the proximal end portion of the connectionmember 12 is sealed to the proximal end portion of the inner tube 35 andthe outer periphery of the distal end portion of the catheter body 32air tightly or liquid tightly. Due to this constitution, the opening 52at the proximal end of the guide wire lumen 51 is formed continuous tothe distal end portion of the groove 21. As shown in FIG. 11, since theguide wire 100 extends linearly in the groove 21 from the guide wirelumen 51, it has low resistance to sliding with the catheter 31, therebymaking it possible to carry out the operation of moving forward orbackward the catheter 31 and the guide wire 100 relative to each othersmoothly.

[0150] The length of the guide wire lumen 51 is not particularly limitedbut is preferably about 3 to 30 cm, more preferably about 7 to 20 cm inconsideration of the operation of exchanging the catheter.

[0151] The structural materials of the connection member 12 and theinner tube 35 are not particularly limited but preferably a polymermaterial having flexibility includes, for example, a polyolefin such aspolyethylene, polypropylene, an ethylene-propylene copolymer, anethylene-vinyl acetate copolymer or a crosslinked ethylene-vinyl acetatecopolymer; thermoplastic or thermosetting resin such as polyester,polyvinyl chloride, polyurethane, polyamide, polyimide, polyamideelastomer, polyurethane elastomer, polyester elastomer, polyfluororesin,or other.

[0152] As shown in FIG. 10, the hub 4 is mounted to the proximal endportion of the catheter body 32. The lumen of the hub 4 communicateswith the proximal end of the balloon lumen 11. A balloon inflatingdevice (not shown) such as a syringe is connected to the hub 4 in orderto supply a working fluid supplied therefrom into the inside of theballoon 33 through the balloon lumen 11 or extract the working fluid,thereby inflating or deflating the balloon 33.

[0153] The working fluid for inflating the balloon is liquid because ithas an advantage that the volume of a liquid does not change even whenpressure is applied to the liquid whereas the volume of a gas decreaseswhen pressure is applied to the gas. In addition, the liquid is usedfrom the viewpoints of reduction of a pressure loss and safety if, byany chance, the balloon ruptures. A liquid having X-ray contrastproperties is preferred as the liquid. For example, a liquid prepared bydiluting an X-ray contrast medium such as a contrast medium for theartery with physiological saline to several folds may be used.

[0154] Preferably, all or part of the surface of the guide wire 100 issubjected to a treatment for providing lubricity, the distal end portionthereof is tapered corresponding to characteristic properties such asbutt resistance and bend resistance, and the outer diameter thereofprogressively decreases toward the distal end. Accordingly, when theguide wire 100 is inserted into the blood vessel from the distal endside thereof to reach the targeted site (the coronary artery, etc.), theinsertion of the guide wire 100 can be performed smoothly and theinsertion operation can be performed easily and safely while flexiblycoping with the complex shape such as curvature or branching of theblood vessel.

[0155] The above catheter 31 and the guide wire 100 are inserted intothe guiding catheter 200 before use. As shown in FIG. 12, the guidingcatheter 200 is a tubular member having flexibility and an innerdiameter larger than the outer diameter of the catheter body 32. Thestructural material of the guiding catheter 200 is not particularlylimited but may be the same as the structural material of the connectionmember 12 and the inner tube 35, for example.

[0156] As shown in FIG. 10, a Y connector 300 is mounted on the proximalend side of the guiding catheter 200. A lumen is formed inside of the Yconnector 300 in the longitudinal direction and this lumen communicateswith the lumen of the guiding catheter 200. The catheter 31 and theguide wire 100 project from the proximal end of the Y connector 300through the lumens of the guiding catheter 200 and the Y connector 300.

[0157] Further, a tubular branched portion 310 is formed on the Yconnector 300. This branched portion 310 is used, for example, to injectan X-ray contrast medium into a desired targeted site in the bloodvessel. The X-ray contrast medium injected from the branched portion 310is discharged from the opening at the distal end of the guiding catheter200 through the lumen of the Y connector 300 and the lumen of theguiding catheter 200.

[0158] The catheter of the present invention has been described abovewith reference to the illustrated embodiments. However, the presentinvention is not limited to these and components constituting thecatheter may be substituted by any arbitrary known components which canexhibit the same functions. Any arbitrary known component may also beadded.

[0159] A description is subsequently given on usage when the catheter 31is applied to PTCA.

[0160] [1] According to the Seldinger method, a catheter introducer isstuck into a femoral artery (or brachial artery), and the guidingcatheter 200 containing a guide wire (not shown) is inserted into theartery from the sheath of the catheter introducer, moved forward orbackward or turned repeatedly while the guide wire precedes the guidingcatheter 200 until the distal end portion thereof reaches the inlet ofthe coronary artery and is left there.

[0161] [2] After the above-mentioned guide wire is pulled out, thecatheter 31 having the guide wire 100 situated in the groove 21 and theguide wire lumen 51 is inserted from a hemostatic valve provided in theopening at the proximal end of the Y connector 300 and moved forwardalong the lumen of the guiding catheter 200 toward the distal enddirection, preceded by the guide wire 100, and the distal end portion ofthe catheter 31 is projected from the opening at the distal end of theguiding catheter 200. In the present invention, as described above, thecatheter 31 can be advanced smoothly and quickly while it is turned asrequired in accordance with the curvature of the guiding catheter 200and the curvature of the blood vessel.

[0162] [3] When the distal end of the catheter 31 reaches the coronaryartery, the guide wire 100 is moved forward while it is turned asrequired so that the distal end thereof passes through the stricture ofthe coronary artery which is the targeted site. In the presentinvention, since the guide wire 100 is received in the groove 21, it isalso turned by the rotation of the catheter 31 described above and isnot twined around the outer periphery of the catheter body 2, therebyimproving the operation ease of the guide wire 100. Therefore, the workof passing the guide wire 100 through the stricture of the coronaryartery can be carried out readily and reliably.

[0163] During this, the X-ray contrast medium is injected from thebranched portion 310 of the Y connector 300 to be supplied into thecoronary artery through the lumens of the Y connector 300 and theguiding catheter 200 to create an image for confirming the position.

[0164] [4] When the distal end of the guide wire 100 has passed throughthe stricture of the coronary artery, the advancement of the guide wire100 is stopped and then the catheter 31 is advanced along the guide wire100 slowly to position the balloon 33 in the stricture of the coronaryartery using the X-ray impermeable markers 15 as a clue.

[0165] Then, the working fluid is injected from the hub 4 to be suppliedinto the balloon 33 through the lumen of the hub 4 and the balloon lumen11 to inflate the balloon 33 at 4 to 18 atm, which differs according tothe size of the balloon 33. Thus, the stricture of the coronary arteryis expanded.

[0166] [5] To further expand the stricture of the coronary artery fromthis state, for example, the inserted catheter is exchanged with acatheter suitable therefor that has a larger balloon.

[0167] To exchange the catheter 31 inserted into the coronary arterywith a new catheter, the balloon 33 is deflated while the guide wire 100and the guiding catheter 200 are left as they are and then the hub 4 ispulled toward the proximal end to retreat the catheter 31 and pull itout. Since the proximal end of the guide wire 100 is fixed by the fingeror the like, the catheter 31 can be pulled out while the guide wire 100is left in the body.

[0168] The proximal end of the guide wire 100 is inserted into a hole atthe distal end of the new catheter to be exchanged (balloon catheter,etc.), and the catheter is moved forward along the guide wire 100 toreach the targeted site through the Y connector 300 and the lumen of theguiding catheter 200 in the same manner as described above. As a result,exchange of the catheter is completed. Thereafter, operation is carriedout according to the purpose of the exchanged catheter.

[0169] The balloon catheter of the present invention has been describedabove with reference to the illustrated embodiments. However, thepresent invention is not limited to these and components constitutingthe balloon catheter may be substituted by any arbitrary knowncomponents which can exhibit the same functions. Any arbitrary knowncomponents may also be added.

EFFECT OF THE INVENTION

[0170] As described above, according to the present invention, there isobtained a catheter which has a simple structure, excellent torquetransmissibility, pushability and followability and allows extremelyhigh ease of operation.

[0171] Further, when the catheter body has a portion where the depth ofthe groove decreases continuously or stepwise toward the proximal endthereof, torque transmissibility, pushability and followability can befurther improved.

[0172] Further, when the groove of the catheter body is formed byplastically transforming the tubular wall of the catheter body, thecatheter can be produced easily and the above-mentioned effect can beobtained at lower production cost.

[0173] Further, when there is provided a tubular member for covering theouter periphery of at least the distal end side portion of the catheterbody, which is made from a synthetic resin material, higher safety isobtained.

[0174] Further, when at least part of the guide wire can be insertedinto the groove of the catheter body, the guide wire can be used incombination with a guiding catheter having a smaller diameter and can beinserted into a narrower blood vessel.

[0175] Furthermore, when the groove of the catheter body is formed byplastically transforming the tubular wall of the catheter body, thecatheter can be produced easily and the above-mentioned effect can beobtained at lower production cost.

What is claimed is:
 1. A catheter having a tubular catheter body madefrom a metal material, wherein the catheter body has a groove formed ina longitudinal direction in the outer periphery of at least the distalend side portion thereof in such a manner that the tubular wall is cavedin; and the thickness of the tubular wall of the catheter body is almostconstant along the entire circumference including the groove formedportion.
 2. A balloon catheter comprising: a tubular catheter body madefrom a metal material; a balloon which can be inflated and deflated andis mounted on the distal end side of the catheter body; a balloon lumenwhich is formed of the lumen of the catheter body and that communicateswith the inside of the balloon; and a guide wire lumen which is open tothe distal end side of the balloon, is surrounded by the tubular wall inthe balloon and has a guide wire inserted from the distal end side ofthe balloon to the outside of the catheter body therein, wherein thecatheter body has a groove formed in a longitudinal direction in theouter periphery of at least the distal end side portion thereof in sucha manner that the tubular wall is caved in; and the thickness of thetubular wall of the catheter body is almost constant along the entirecircumference including the groove formed portion.
 3. A catheteraccording to claim 1, wherein the groove is formed along almost theentire length of the catheter body.
 4. A balloon catheter according toclaim 2, wherein the groove is formed along almost the entire length ofthe catheter body.
 5. A catheter according to claim 1 which has aportion where the depth of the groove decreases continuously or stepwisetoward the proximal end.
 6. A balloon catheter according to claim 2which has a portion where the depth of the groove decreases continuouslyor stepwise toward the proximal end.
 7. A balloon catheter according toclaim 2, wherein the at least part of the guide wire can be insertedinto the groove.
 8. A balloon catheter according to claim 2, wherein anopening at the proximal end of the guide wire lumen is formed continuousto the distal end portion of the groove.
 9. A balloon catheter accordingto claim 2, wherein an inner tube is inserted into the balloon and theguide wire lumen is formed of the lumen of the inner tube.
 10. Acatheter according to claim 1, wherein the catheter body is made fromstainless steel or pseudoelastic alloy.
 11. A balloon catheter accordingto claim 2, wherein the catheter body is made from stainless steel orpseudoelastic alloy.
 12. A catheter according to claim 1 furthercomprising a tubular member, made from a synthetic resin material, forcovering the outer periphery of at least the distal end side portion ofthe catheter body and extending farther in the distal end direction thanthe distal end of the catheter body.
 13. A balloon catheter according toclaim 2 further comprising a tubular member, made from a synthetic resinmaterial, for covering the outer periphery of at least the distal endside portion of the catheter body and extending farther in the distalend direction than the distal end of the catheter body.
 14. A catheteraccording to claim 1, wherein plural slits are formed in the tubularwall of the distal end side portion of the catheter body and extend in adirection almost perpendicular to the longitudinal direction of thecatheter body.
 15. A balloon catheter according to claim 2, whereinplural slits are formed in the tubular wall of the distal end sideportion of the catheter body and extend in a direction almostperpendicular to the longitudinal direction of the catheter body.
 16. Acatheter according to claim 1, wherein spiral slits are formed in thetubular wall of the distal end side portion of the catheter body andwherein the spiral pitch between the spiral slits become smallercontinuously or stepwise toward the distal end.
 17. A balloon catheteraccording to claim 2, wherein spiral slits are formed in the tubularwall of the distal end side portion of the catheter body and wherein thespiral pitch between the spiral slits become smaller continuously orstepwise toward the distal end.